Theme C

How does the ozone hole impact global climate and what are the observable indicators?

As ozone depletion recovers over the next 50 years we have an unprecedented chance to observe how the global climate system relaxes from a known perturbation and thereby parse the distinct climate impacts of ozone versus other GHGs versus natural climate variability.

Specific research thrusts include:

Running ensemble simulations to determine climate system sensitivities to varying GHG and ozone-depletion forcing and tease them apart.

Seeking evidence of these ozone impact indicators in the observational record and in climate change projections.

Key results to date:

Expected sea surface warming around Antarctica due to globally rising GHG concentrations appears currently to be offset by short-term cooling associated with the ozone hole. By mid-Century, however, longer term ozone hole impacts may well add to background GHG warming, albeit with diminishing strength as the ozone hole heals.See Marshall et al. 2014>

Three decades of data indicate strong correspondence between high levels of stratospheric ozone over Antarctica during November with unusually warm, dry and heat wave prone summers in mid-latitude areas of Australia, South America and Africa. This relationship could potentially be exploited to enhance extended summer weather forecasting for these areas.See Bandoro et al. 2014>

The poleward migration and increasing intensity of southern hemispheric westerly winds (jets) over the past few decades cannot be explained by natural variability alone. Changes in external forcing (e.g. ozone hole, rising GHG concentrations) appear to play a critical role, suggesting that trends in jet location and magnitude may provide a sensitive diagnostic for analyzing the impacts of changes in forcing.See Thomas et al. 2015>

Observational evidence indicates that the southern edge of the Hadley Cell has shifted southward during austral summer in recent decades. We performed a meta-analysis of published studies that have used single-forcing model integrations to isolate the role of different factors causing this shift. It is shown that stratospheric ozone depletion is the dominant driver over the period in which an ozone hole was formed (1979 to late 1990s), although sea surface temperature trends have contributed since then.See Waugh et al. 2015>